ProjectSummary Understandinghowchildrenlearnandespeciallyunderstandinghowchildrenlearnlanguage isa critical public health issue. Positive academic outcomes (which are predicted by early language skill) are associatedwithpositivehealthoutcomeslikelowerratesofsubstanceabuse,higherratesofoffspringsurvival, higheroccupationalsuccess,andlongerlifespans(Hawkins,Catalano,&Miller,1992?Low,Low,Baumler,& Huynh, 2005? McGregor et al., 2007? Serbin, Stack, & Kingdon, 2013). While we know that early social, cognitive, and language ability predict educational outcomes (McGregor et al., 2007? Marchman & Fernald, 2008), many basic questions about early child development remain unanswered, making it challenging to designeffectiveearlyeducationalpolicyandinterventions.Oneimportantquestionishowachild?sinput(e.g., thethingsthattheyseeandhearindailylife)predictswhattheyenduplearning.Thisquestionisrelevantto researchersinterestedinallaspectsofdevelopment.Answeringsuchaquestion,however,requiresactually measuringachild?sinputsomethingthatuntilrecentlywastechnologicallyimpossible.PISullivanandDrs. Frank and Perfors (see letters of support) created a large longitudinal dataset of videos from the child?s perspectivetomeasureinput.Ourgoalistomakethisdatasetavailableandaccessibletootherresearchers. Usingaheadmountedcamera,werecordedeverythingthatparticipantssawandheardfromtheir perspective for approximately 2.5 hours a week over the course of two years (from infancy through toddlerhood),andcontinuedthroughtoddlerhood.Recordingswerenaturalistic,andincludedawidearrayof contextsandactivitiesthathaveneverpreviouslybeenrecorded.Thisresultedinadatasetofover325hours ofaudiovisualrecordings,alongwithadensecollectionofcognitive,social,andlinguisticmeasuresthatwere also collected longitudinally. This dataset is the first of its kind, and is unique in its size, scope, and perspective. ThisR03proposalhasthreemainaims.First,weaimtoposttheentiretyofourdatasettoDatabrary, anNIHfundedhostforvideodatarelevanttochilddevelopmentresearch.Thiswillallowotherresearchersto accessourrichdataset.Thiswillrequireconvertingthevideosintoastandardizedformatandcollaborating withDatabrarytohostthevideos.Oursecondaimistoattachtheappropriatemetadatatothevideossothat theycanbesearchablebyresearchers.Tothisend,wewillhireafulltimeresearchassistantwhowillcreatea databaseofbothvideoleveldata(e.g.,thetimeofdayandyear,thechild?sage,thepeoplefeaturedinthe video)andtimestampeddata(e.g.,namesoflocations,activities,andobjectssalientinthechild?svisualfield). Third,wewilltranscribeandprovideadetailedcodingofasizeablesubsetofourcorpus(includingverbatim transcriptions,descriptionsoftheobjectsbeingtouchedandseen,andcodingofthereferentsofeachspeech act)thatwillallowotherresearcherstoimmediatelybeginansweringquestionsofourdata.